The present invention relates to radiolabeled compounds and their method of use in clinical nuclear medicine. More specifically, the present invention relates to radioiodinated meta-iodobenzylguanidine and its method of use as an imaging agent, particularly for the heart, adrenal medulla, and tumors of the adrenal medulla. In addition, the present invention relates to the method of use of radioiodinated meta-iodobenzylguanidine as a treatment agent for tumors of the adrenal medulla.
Radiolabeled compounds which are subject to localization in particular organs or tumors therein are of great value for diagnosis and/or therapeutic purposes for diseases of the human body. For example, Thallium-201 and fatty acids labeled with carbon-11 and iodine-123 have been utilized as heart imaging agents. Also, various phosphonate ligands labeled with technetium-99m have been used to image infarcted regions of the heart. However, although many useful radiolabeled compounds are known, there remains a need for the discovery of additional or improved compounds which are effective for routine imaging of particular organs, tissues, or tumors therein. In addition, there remains an obviious need for radiolabeled compounds which are useful in treating tumors of specific organs of the human body.
Although the agent I-131-6B-idodomethyl-19-norcholest-5-(10)-en-3B-ol has been and is being used for imaging the adrenal cortex and its tumors, before the present invention no radiolabeled compound was known which could routinely image the adrenal medulla or tumors of the adrenal medulla. The adrenal medulla, although anatomically contiguous with the adrenal cortex, is an entirely separate tissue both embryolagically and functionally. Hence, the need for an agent effective to image the adrenal medulla is readily apparent.
There is also a need for an improved imaging agent for the heart. Although thallium-201 is used for heart imaging, it is expensive and has less than optimum nuclear imaging properties. Carbon-11 fatty acids can be used for heart imaging but their use is severely limited by the requirement for an in-house cyclotron for the product of the short-lived isotope (Tl/2=20 min) C-11. The use of iodine-123 fatty acids is still being evaluated in various nuclear medicine clinics throughout the world, but these compounds have a short biologic Tl/2 (about 10 minutes) in the heart. Technetium-99m labeled diphosphonates are useful heart imaging agents but are not heart perfusion agents and are limited to imaging only severely damaged or infarcted regions of the heart.
Accordingly, the present invention provides a novel radiopharmeceutical compound, radioiodinated metaiodobenzylguanidine, and its method of use as an exceptional imaging agent, particularly for the adrenal medulla, tumors of the adrenal medulla and the heart. A method of using radioiodinated meta-iodobenzylguanidine as a therapeutic agent for the treatment of tumors, particularly tumors of the adrenal medulla, is also provided by the present invention.